Analysis of Cooperative Spatial Multiplexing for Ad Hoc Networks with Adaptive Hybrid ARQ

Existing cooperative diversity techniques for wireless ad hoc networks mostly consider space-time block codes for cooperation. In this paper we propose a cross-layer design of ad hoc wireless networks based on spatial multiplexing (SM). Each node is equipped with multiple antennas and the spatial dimensions of the channel are exploited to support multiple simultaneous transmissions. Diversity is then provided only for failed transmissions by means of selective cooperation among nodes that still use SM for transmission. Moreover, to increase the efficiency of the system, a hybrid automatic repeat request (HARQ) protocol integrated with packet coding is used at the medium access control layer. We analyze the proposed network architecture with a Markov chain description of the decoding process and we derive a closed form expression for the achieved throughput in Rayleigh fading channels.